Method and apparatus for wireless network hybrid positioning

ABSTRACT

Methods and apparatuses for position determination and other operations. In one embodiment of the present invention, a mobile station uses wireless signals from a plurality of wireless networks (e.g., with different air interfaces and/or operated by different service providers) for position determination (e.g., for data communication, for obtaining time and/or frequency information, for range measurement, for sector or altitude estimation). In one embodiment of the present invention, mobile stations are used to harvest statistical data about wireless access points (e.g., the locations of mobile stations that have received signals from the wireless access points, such as from cellular base stations, wireless local area network access points, repeaters for positioning signals, or other wireless communication transmitters) and to derive location information (e.g., position and coverage area of the wireless access points) for the wireless networks from the collected statistical data.

This application is a continuation of U.S. patent application Ser. No.14/505,053, filed Oct. 2, 2014, which is a divisional of U.S. patentapplication Ser. No. 10/877,205, filed Jun. 25, 2004, now U.S. Pat. No.8,971,913, issued Mar. 3, 2015, which claims the benefit of U.S.Provisional Patent Application Ser. No. 60/483,094, filed Jun. 27, 2003,each of which is expressly incorporated by reference herein in itsentirety.

FIELD OF THE INVENTION

The invention relates to position determination systems, and moreparticularly to hybrid positioning using wireless communication signals.

BACKGROUND

To perform position location in wireless cellular networks (e.g., acellular telephone network), several approaches perform trilaterationbased upon the use of timing information sent between each of severalbase stations and a mobile device, such as a cellular telephone. Oneapproach, called Advanced Forward Link Trilateration (AFLT) in CDMA orEnhanced Observed Time Difference (EOTD) in GSM or Observed TimeDifference of Arrival (OTDOA) in WCDMA, measures at the mobile devicethe relative times of arrival of signals transmitted from each ofseveral base stations. These times are transmitted to a Location Server(e.g., a Position Determination Entity (PDE) in CDMA), which computesthe position of the mobile device using these times of reception. Thetransmit times at these base stations are coordinated such that at aparticular instance of time, the times-of-day associated with multiplebase stations are within a specified error bound. The accurate positionsof the base stations and the times of reception are used to determinethe position of the mobile device.

FIG. 1 shows an example of an AFLT system where the times of reception(TR1, TR2, and TR3) of signals from cellular base stations 101, 103, and105 are measured at the mobile cellular telephone 111. This timing datamay then be used to compute the position of the mobile device. Suchcomputation may be done at the mobile device itself, or at a locationserver if the timing information so obtained by the mobile device istransmitted to the location server via a communication link. Typically,the times of receptions are communicated to a location server 115through one of the cellular base stations (e.g., base station 101, or103, or 105). The location server 115 is coupled to receive data fromthe base stations through the mobile switching center 113. The locationserver may include a base station almanac (BSA) server, which providesthe location of the base stations and/or the coverage area of basestations. Alternatively, the location server and the BSA server may beseparate from each other; and, the location server communicates with thebase station to obtain the base station almanac for positiondetermination. The mobile switching center 113 provides signals (e.g.,voice communications) to and from the land-line Public SwitchedTelephone Network (PSTN) so that signals may be conveyed to and from themobile telephone to other telephones (e.g., land-line phones on the PSTNor other mobile telephones). In some cases the location server may alsocommunicate with the mobile switching center via a cellular link. Thelocation server may also monitor emissions from several of the basestations in an effort to determine the relative timing of theseemissions.

In another approach, called Uplink Time of Arrival (UTOA), the times ofreception of a signal from a mobile device is measured at several basestations (e.g., measurements taken at base stations 101, 103 and 105).FIG. 1 applies to this case if the arrows of TR1, TR2, and TR3 arereversed. This timing data may then be communicated to the locationserver to compute the position of the mobile device.

Yet a third method of doing position location involves the use in themobile device of circuitry for the United States Global PositioningSatellite (GPS) system or other Satellite Positioning Systems (SPS),such as the Russian GLONASS system and the proposed European GalileoSystem, or a combination of satellites and pseudolites. Pseudolites areground-based transmitters, which broadcast a PN code (similar to a GPSsignal) modulated on an L-band carrier signal, generally synchronizedwith SPS time. Each transmitter may be assigned a unique PN code so asto permit identification by a mobile device. Pseudolites are useful insituations where SPS signals from an orbiting satellite might beunavailable, such as tunnels, mines, buildings or other enclosed areas.The term “satellite”, as used herein, is intended to include pseudoliteor equivalents of pseudolites, and the term GPS signals, as used herein,is intended to include GPS-like signals from pseudolites or equivalentsof pseudolites. Methods which use an SPS receiver to determine aposition of a mobile station may be completely autonomous (in which theSPS receiver, without any assistance, determines the position of themobile station) or may utilize the wireless network to provideassistance data or to share in the position calculation. Examples ofsuch methods are described in U.S. Pat. Nos. 6,208,290; 5,841,396;5,874,914; 5,945,944; and 5,812,087. For instance, U.S. Pat. No.5,945,944 describes, among other things, a method to obtain fromcellular phone transmission signals accurate time information, which isused in combination with SPS signals to determine the position of thereceiver; U.S. Pat. No. 5,874,914 describes, among other things, amethod to transmit the Doppler frequency shifts of in view satellites tothe receiver on the mobile device through a communication link todetermine the position of the mobile device; U.S. Pat. No. 5,874,914describes, among other things, a method to transmit satellite almanacdata (or ephemeris data) to a receiver through a communication link tohelp the receiver to determine its position; U.S. Pat. No. 5,874,914also describes, among other things, a method to lock to a precisioncarrier frequency signal of a cellular telephone system to provide areference signal at the receiver for SPS signal acquisition; U.S. Pat.No. 6,208,290 describes, among other things, a method to use anapproximate location of a receiver to determine an approximate Dopplerfor reducing SPS signal processing time; and, U.S. Pat. No. 5,812,087describes, among other things, a method to compare different records ofa satellite data message received to determine a time at which one ofthe records is received at a receiver in order to determine the positionof the receiver. In practical low-cost implementations, both the mobilecellular communications receiver and the SPS receiver are integratedinto the same enclosure and, may in fact share common electroniccircuitry.

In yet another variation of the above methods, the round trip delay(RTD) is found for signals that are sent from the base station to themobile device and then are returned. In a similar, but alternative,method the round trip delay is found for signals that are sent from themobile device to the base station and then returned. Each of theseround-trip delays is divided by two to determine an estimate of theone-way propagation delay. Knowledge of the location of the basestation, plus a one-way delay constrains the location of the mobiledevice to a circle on the earth. Two such measurements from distinctbase stations then result in the intersection of two circles, which inturn constrains the location to two points on the earth. A thirdmeasurement (even an angle of arrival or cell sector identification)resolves the ambiguity.

A combination of either the AFLT or U-TDOA with an SPS system may bereferred to as a “hybrid” system. For example, U.S. Pat. No. 5,999,124describes, among other things, a hybrid system, in which the position ofa cell based transceiver is determined from a combination of at least:i) a time measurement that represents a time of travel of a message inthe cell based communication signals between the cell based transceiverand a communication system; and, ii) a time measurement that representsa time of travel of an SPS signal.

Altitude aiding has been used in various methods for determining theposition of a mobile device. Altitude aiding is typically based on apseudo-measurement of the altitude. The knowledge of the altitude of alocation of a mobile device constrains the possible positions of themobile device to a surface of a sphere (or an ellipsoid) with its centerlocated at the center of the earth. This knowledge may be used to reducethe number of independent measurements required to determine theposition of the mobile device. For example, U.S. Pat. No. 6,061,018describes, among other things, a method where an estimated altitude isdetermined from the information of a cell object, which may be a cellsite that has a cell site transmitter in communication with the mobiledevice.

SUMMARY OF THE DESCRIPTION

In one aspect of the present invention, a method to determineinformation about a wireless access point includes: communicatingbetween a server and one or more mobile stations through one or morefirst wireless access points of a first wireless network for locationdetermination of the one or more mobile stations; collecting dataspecifying a plurality of locations from which wireless signalstransmitted from a second wireless access point of a second wirelessnetwork are received by the one or more mobile stations wherein thesecond wireless network is different than the first wireless network;and determining location information about the second wireless accesspoint from the data. The location information may include an estimatedposition of the second wireless access point. This estimated position ofthe second wireless access point may be determined from a weightedaverage of the plurality of locations; a weight for the weighted averagemay be based on positioning information which indicates a distancebetween a corresponding one of the plurality of locations to the secondwireless access point of the second wireless network. The positioninginformation may be an indicator of received signal level for signalstransmitted from the second wireless access point and received at amobile station at the corresponding one of the plurality of locations.In one exemplary implementation, the location information includes acoverage area of the second wireless access point and an estimatedposition of the second wireless access point which is determined fromthe coverage area of the second wireless access point. In certainexemplary implementations, positioning information such as ranges thatspecify distances between each of the plurality of locations and thesecond wireless access point of the second wireless network may befurther collected; and, the location information includes an estimatedposition of the second wireless access point, which is determined fromthe range information and the data collected.

In another aspect of the present invention, a method to determineinformation about a wireless network includes: collecting dataspecifying a plurality of locations of mobile stations at which wirelesssignals transmitted from a first wireless access point of a firstwireless network are received during determination of the plurality oflocations, the mobile stations receiving signals from the first wirelessaccess point and also communicating signals between the mobile stationsand at least a second wireless point of a second wireless network whichis different than the first wireless network; and determining a locationof the first wireless access point from a coverage area defined by theplurality of locations. In one example of this method, statistics of anymobile station being in an area in which wireless signals transmittedfrom the first wireless access point can be received during positiondetermination is determined. The location of the wireless access pointmay be determined from a weighted average of the plurality of locations;and a weight for the weighted average is based on an indicator ofreceived signal level for signals transmitted from the wireless accesspoint and received by a mobile station at a corresponding one of theplurality of locations. The first wireless access point may operate inaccordance with a standard for a wireless local area network (e.g., IEEE802.11).

In another aspect of the present invention, a method for a mobilestation of a position determination system includes: determining, at themobile station, first identification information of a first wirelessaccess point of a first wireless network; determining first positioninformation that relates to a first position of the mobile station in asignal coverage area of the first wireless access point; andcommunicating first data indicating a correlation between the firstidentification information and the first position information from themobile station to a server which is remote to the first wireless accesspoint. The communicating is through a second wireless access point of asecond wireless network which is different than the first wirelessnetwork. In one example of this method, first position informationindicates a distance between the first position of the mobile stationand a position of the first wireless access point, and this firstposition information is determined and transmitted as a part of thefirst data. The first position information may be an indication of asignal level for signals that are transmitted from the first wirelessaccess point and received at the first position by the mobile station.Alternatively, the first position information may be an actual position(for example, one determined through a GPS “fix”). The first positioninformation may include one of: a) a measurement of a distance betweenthe first position of the mobile station and the position of the firstwireless access point; b) a measurement of a time delay in signaltransmission from the first wireless access point to the mobile stationat the first position; and c) a measurement of a round trip time delayfor signal transmission between the first wireless access point and themobile station at the first position. In one example, the first wirelessaccess point is an access point of a local area network (e.g., an IEEE802.11 wireless LAN); and, the first identification information includesa Media Access Control (MAC) address. In one example, the first wirelessaccess point supports two-way communication. In one example, SatellitePositioning System (SPS) signals from at least one SPS satellite isreceived to determine the first position information (which may includea measurement of pseudorange to an SPS satellite).

In one example, the first data is communicated to the server through thefirst access point. In another example, the first data is communicatedto the server through a second wireless access point, where the firstwireless access point is an access point of a local area network andwhere the second wireless access point is a cellular base station. Inone example, the mobile station further determines: i) secondidentification information of a second wireless access point, and ii)second position information that indicates a second position of themobile station in a signal coverage area of the second wireless accesspoint; and then, second data indicating a correlation between the secondidentification information and the second position is communicated fromthe mobile station to the server. In one example, the first and seconddata are communicated from the mobile station to the server through acellular base station. In one example, the mobile station determinessecond identification information of another wireless access point andcommunicates the second identification information from the mobilestation to the server to determine a second position of the mobilestation in a signal coverage area of the second wireless access point;where the first and second wireless access points may be a same accesspoint (e.g., both the first data and the second identification arecommunicated from the mobile station to the server through a cellularbase station).

The present invention includes methods and apparatuses which performthese methods, including data processing systems which perform thesemethods, and computer readable media which when executed on dataprocessing systems cause the systems to perform these methods. Further,the inventions described herein may be implemented on different nodeswithin a system, such nodes including a mobile station, a base station(such as a wireless access point) or a location server or other nodes ina network or wireless network.

Other features of the present invention will be apparent from theaccompanying drawings and from the detailed description which follows.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is illustrated by way of example and notlimitation in the figures of the accompanying drawings in which likereferences indicate similar elements.

FIG. 1 shows an example of a prior art cellular network which determinesthe position of a mobile cellular device.

FIG. 2 shows an example of a server which may be used with the presentinvention.

FIG. 3 shows a block diagram representation of a mobile stationaccording to one embodiment of the present invention.

FIG. 4 shows one example of a hybrid positioning system according to oneembodiment of the present invention.

FIG. 5 shows another example of a hybrid positioning system according toone embodiment of the present invention.

FIG. 6 illustrates one method to determine the position of a wirelessaccess point according to one embodiment of the present invention.

FIG. 7 illustrates another method to determine the position informationof a wireless access point according to one embodiment of the presentinvention.

FIG. 8 shows a method of hybrid position determination using a pluralityof wireless networks according to one embodiment of the presentinvention.

FIG. 9 shows a method of hybrid position determination using twowireless networks for communication with a server according to oneembodiment of the present invention.

FIG. 10 shows a method to generate location information about a wirelessaccess point according to one embodiment of the present invention.

FIG. 11 shows a hybrid position determination method using one wirelessnetwork for communication and another wireless network for themeasurement of positioning parameters according to one embodiment of thepresent invention.

FIG. 12 is a flowchart showing another exemplary embodiment of theinvention.

FIG. 13 is a flowchart showing another exemplary embodiment of theinvention.

FIG. 14 is a flowchart showing another exemplary embodiment of theinvention.

DETAILED DESCRIPTION

The following description and drawings are illustrative of the inventionand are not to be construed as limiting the invention. Numerous specificdetails are described to provide a thorough understanding of the presentinvention. However, in certain instances, well known or conventionaldetails are not described in order to avoid obscuring the description ofthe present invention. References to one or an embodiment in the presentdisclosure are not necessary to the same embodiment; and, suchreferences mean at least one.

Recent development of wireless communication technologies leads to thedeployment of various different wireless networks with substantialoverlapping coverage in some areas. In the present application, awireless network refers to a set of wireless access points (e.g., basestations) with a same air interface, operated by one service provider(e.g. Verizon Wireless or Sprint), such that a mobile unit can accessthe network through one of the set of the wireless access points when inthe coverage area of the network; and, the union of the coverage areasof the wireless access points of the wireless network is the coveragearea of the network. Further, data communication refers to thetransmission of data in a two-way communication system although, incertain embodiments, data communication may be a one-way communicationor may include extracting information embedded in a signal which isbroadcasted regardless whether the receiver needs it or not. A wirelessaccess point may be considered to be a cell tower or a base station orother wireless transmitter or receiver which is coupled to a network ofother nodes (for example, the wireless access point is coupled bywireless or wire line to the other nodes).

In certain areas, especially urban metropolitan areas, differentwireless networks have substantially overlapping coverage. For example,different service providers may offer the same type of wireless service(e.g., cellular phone communication) in the same area. Further,different types of wireless services, such as wireless phone services(e.g., cellular phone services for data, voice or both) and wirelessdigital communication services (e.g., wireless local area networks suchas Wi-Fi networks, bluetooth, ultra-wideband), may have overlapping incoverage area. For example, wireless LAN (Local Area Network) accesspoints (e.g., for an IEEE 802.11 based wireless network) may be locatedwithin the coverage areas of wireless telecommunication networks (e.g.,based on Telecommunications Industry Association (TIA)/ElectronicIndustries Alliance (EIA) Standards, such as IS-95, IS-856 or IS-2000),such as those based on TDMA (Time Division Multiple Access), GSM (GlobalSystem for Mobile communications), CDMA (Code Division Multiple Access),WCDMA (Wideband Code Division Multiple Access), UMTS (United MobileTelecommunication System), TD-SCDMA (Time Division Synchronous CodeDivision Multiple Access), iDEN (Integrated Digital Enhanced Network),HDR (High Data Rate), or other similar cellular networks.

At least one embodiment of the present invention seeks a comprehensivesystem which supports positioning using these disparate sources ofwireless signals to determine measurements and to obtain aidinginformation (e.g., the position and the coverage area of an accesspoint, Doppler frequency shifts for in view SPS satellites, SPSephemeris data) to form a flexible and ubiquitous navigation solution.In this comprehensive system, when information about an access point(e.g., base station almanac, such as the location and coverage area ofthe base station) is available, it is used and may be enhanced. Where itis not, the system may automatically gather and enhance such informationfor the benefit of future positioning attempts.

At least one embodiment of the present invention uses wireless signalstransmitted from access points of more than one wireless network tocombine information, such as SPS observations, wireless networkobservations, terrain elevation information and others, to obtain aposition solution for a mobile station. In one embodiment of the presentinvention, a mobile station of a hybrid position system transfersinformation over access points of more than one wireless network (intwo-way communication) to aid in the acquisition of SPS signals, timestamping for measurements and other operations at the mobile station. Inone embodiment of the present invention, a mobile station of a hybridposition system performs measurements using signals from access pointsof different wireless networks, while communicating with a remote serverusing one or more of the wireless networks.

Typically, information describing the identification, location, andcoverage area of the sectors of a wireless network is stored in a basestation almanac, which has been used in a hybrid positioning systemusing a single wireless network. However, when different wirelessnetworks (e.g., different service providers or different types ofnetworks) have overlapping coverage, a typical mobile station does nothave access to such information for the access points of the differentwireless networks, even though the wireless signals transmitted from theaccess points of the different wireless networks are in the air andavailable to the mobile station. This is usually because the mobilestation is allowed or is authorized to have access to one wirelessnetwork but not another wireless network. One simple example of this isa cell phone which has been authorized access to a first wirelessnetwork (e.g. a cell phone network operated by a service provider suchas Verizon Wireless) but has not been authorized access to a secondwireless network (e.g. Sprint's cell phone network) or to a thirdwireless network (e.g. a Wi-Fi “hotspot”).

In one embodiment of the present invention, when available, informationfrom small and localized transmitters, such as an IEEE 802.11 wirelessLAN access point, is incorporated into the wireless navigation solution.In many cases, the location information for these transmitters is notwell known. In some cases, the “almanac” information describing thephysical characteristics of a wireless network (e.g. ID, location, andcoverage area of access points) is not available to users who might liketo use it. Some network providers may choose not to share suchinformation, while still others may not have it available. In oneembodiment of the present invention, information for deriving thephysical characteristics of a network is gathered from mobile stationsthat use another wireless network for communication. In one embodimentof the present invention, using the wireless signals available in theair from different wireless networks and the abilities of the mobilestation for position determination (e.g. a cell phone with a GPSreceiver or with a portion of a GPS receiver), mobile stations harvestinformation about the access points of the different wireless networks,which in general may not be under control of an operator of a wirelessnetwork through which the mobile stations typically perform datacommunication. The harvested information is used to derive locationinformation (e.g., the location, coverage area) about the access points,which can be used for aiding hybrid position determination for futureposition determinations.

In one embodiment of the present invention, the signals used to providetime information and/or frequency information to a mobile station arenot the same as the one over which data communication transactions arecarried out.

A mobile station that supports multiple wireless communicationinterfaces (e.g., IEEE 802.11 [and other IEEE 802 standards such as802.15, 802.16, and 802.20], bluetooth, UWB [Ultra-Wideband], TDMA, GSM,CDMA, W-CDMA, UMTS, TDSCDMA, IDEN, HDR, or other similar networks) isused in one embodiment of the present invention to use multiple wirelessnetworks. Such a mobile station may have, for example, several differentportions in a communication section which support the transmissionand/or reception of data for these different communication interfaces.Thus, one portion may handle the transmission and/or reception of Wi-Fisignals (e.g. IEEE 802.11 or 802.16) and another portion of thecommunication section may support a cellular telephone interface such asa CDMA interface. This also gives the user alternative communicationpaths from which to choose when deciding to communicate. For example,the availability, coverage, expense, data speed, and ease of use may beconsidered when choosing which communication path to use.

In one embodiment of the present invention, a first wireless network isused for communications and positioning, while a second wireless networkis used for positioning and optionally communications. For example, eachof these wireless networks might use a completely different airinterface (e.g., different TIA/EIA standards), such as an air interfacethat is for a typical wireless cell phone (e.g. TDMA, GSM, CDMA, W-CDMA,UMTS, TD-SCDMA, IDEN, HDR, or other similar cellular networks) or someother wireless air interface, such as that in accordance with IEEE802.11, bluetooth or UWB. A plurality of these wireless networks is usedfor positioning purposes, even when only one wireless network may beused for communications. The advantages of a hybrid approach accordingto at least some of the embodiments of the present invention include:improved redundancy for a more fail-safe solution, higher positioningavailability, better accuracy, and faster time to fix.

FIG. 4 shows one example of a hybrid positioning system according to oneembodiment of the present invention. In FIG. 4, mobile station 407utilizes signals in the air that are transmitted from both wirelessaccess point 403 of wireless network A and wireless access point 405 ofwireless network B for position determination. In one embodiment of thepresent invention, the mobile station includes a receiver for receivingSPS signals from SPS satellites (e.g., GPS satellites, not shown in FIG.4). Timing measurements (e.g., pseudorange, round trip time, times ofarrival of signals, time differences of arrival of signals) based on thewireless signals from one or both of wireless networks A and B (and SPSsignals) may be used to determine the position of the mobile station. Itis understood that, in general, each of wireless networks A and Bincludes a number of access points (e.g., cellular base stations such aswireless access points 403 and 405). Wireless networks A and B may usethe same type of air interface, operated by different service providersor they may operate with the same communication protocols but atdifferent frequencies. However, wireless networks A and B may also usedifferent types of air interfaces (e.g., TDMA, GSM, CDMA, W-CDMA, UMTS,TD-SCDMA, IDEN, HDR, bluetooth, UWB, IEEE 802.11, or other similarnetworks), operated by the same service provider or by different serviceproviders.

In one embodiment of the present invention, the position determinationis performed at location server 411 shown in the example depicted inFIG. 4. Mobile station 407 communicates the information extracted fromthe observed SPS signals (e.g., SPS pseudorange measurements, a recordof an SPS message for comparison to determine a time of signalreception) and the information extracted from the observed wirelesssignals (e.g., the identification of an access point, round trip orone-way time measurements between mobile station 407 and at least one ofthe wireless access points, received signal levels) to the locationserver through one of the wireless networks, such as wireless network A(e.g., when the mobile station is a subscriber of wireless network A butnot a subscriber of wireless network B). Servers 413 and 415 maintainthe almanac data for wireless networks A and B respectively. Thisalmanac data may simply be, in one exemplary implementation, a databaselisting a latitude and longitude for each wireless access point which isspecified by an identification information (e.g. MAC address or celltower identifier, etc.). Location server 411 uses the informationcommunicated from the mobile station and the data in the almanac servers413 and 415 to determine the position of the mobile station. Thelocation server 411 may determine the location of the mobile station ina number of different ways. It may, for example, retrieve from servers413 and 415 the locations of wireless access points 403 and 405 and usethose locations and the range measurements, which indicate a distancebetween the mobile station 407 and the points 403 and 405, and the SPSpseudorange measurements and SPS ephemeris information to calculate aposition of the mobile station 407. U.S. Pat. No. 5,999,124 provides adiscussion of how range measurements from a single wireless network andSPS pseudorange measurements may be combined to calculate a position ofa mobile station. Alternatively, the location server 411 may use onlyterrestrial range measurements (or other types of measurements such assignal strength measurements) to multiple wireless access points ofmultiple wireless networks to calculate the position if many (e.g. morethan 3) such range measurements can be made; in this case, there is noneed to obtain SPS pseudoranges or SPS ephemeris information. If SPSpseudoranges to SPS satellites are available, these pseudoranges can becombined with SPS ephemeris information, obtained either by the mobilestation or by a collection of GPS reference receivers as described inU.S. Pat. No. 6,185,427, to provide additional information in theposition calculations.

Network 401 may include local area networks, one or more intranets andthe Internet for the information exchange between the various entities.It is understood that servers 411, 413 and 415 may be implemented as asingle server program, or different server programs in a single dataprocessing system or in separate data processing systems (e.g.,maintained and operated by different service providers).

In one embodiment of the present invention, different service providersoperate wireless networks A and B, which are used by the mobile stationfor position determination. A typical mobile station is a subscriberonly to one of them, and thus the mobile station is authorized to use(and to have access to) only one wireless network. However, it is oftenstill possible to at least receive signals from the wireless networkwhich is not subscribed to and thus it is still possible to make rangemeasurements or signal strength measurements relative to wireless accesspoints in the wireless network which is not subscribed to. One specificexample of this situation would involve a user of a tri-mode CDMAcellular phone which can receive PCS frequency band signals (such as,for example, from the wireless network operated by Sprint, which is afirst service provider) and can also receive other CDMA signals at otherfrequencies (such as, for example, from the wireless network operated byVerizon Wireless, which is a second service provider). If the user hassubscribed only to Sprint's wireless network, then the user's phone (aform of a mobile station) is authorized to operate with Sprint'swireless network but not Verizon's wireless network. The user may usethe phone in an environment in which only one Sprint wireless accesspoint (e.g. a Sprint cellular base station) is capable of radiocommunication with the user's phone, but in this environment there arenumerous Verizon wireless access points which are within radiocommunication range of the user's phone. In this context, it is stillpossible for the phone to obtain SPS assistance data (if desired) from alocation server through Sprint's wireless network and to transmit SPSpseudoranges, obtained at the phone, to the location server. However, itwill not be possible to obtain more than one range measurement to awireless access point unless range measurements to Verizon's wirelessaccess points are obtained. With an embodiment of the invention, thephone obtains range measurements to the available Verizon wirelessaccess points, thereby providing at least a few range measurements (e.g.distances between the phone and two Verizon cellular base stations)which can be used in the position calculations that are performed todetermine the position of the phone.

The service providers maintain the almanac information on servers 413and 415 separately. Although mobile station 407 has communication accessto only one of the wireless networks, location server 411 may haveaccess to both servers 413 and 415 for base station almanac data. Afterdetermining the identities of base stations (e.g. the wireless accesspoints 403 and 405) of both wireless networks A and B, the mobilestation 407 transmits the base station identifications to locationserver 411, which uses servers 413 and 415 to retrieve the correspondingpositions of the base stations, which can be used in determining theposition of the mobile station.

Alternatively, the cooperation between the service providers to sharealmanac data is not necessary. For example, the operator of locationserver 411 maintains both almanac servers 413 and 415 (e.g., through asurvey process to obtain the almanac data, or through a data harvestingprocess using mobile stations, which will be described in detail withFIGS. 6 and 7 and 10).

In one embodiment of the present invention, mobile station 407 uses bothwireless networks A and B for communicating with the location server(instead of using only one of the wireless networks for communicationpurpose). As known in the art, various types of information can beexchanged between the mobile station and the location server forposition determination. For example, location server 411 can provide themobile station 407 with Doppler frequency shift information for in viewsatellites of the mobile station (e.g., through wireless network A);and, the mobile station can provide pseudorange measurements for SPSsignals, the identification information of the base stations andassociated range measurements (e.g., round trip time measurements) tothe location server for the calculation of the position of the mobilestation (e.g., through wireless network B). In one embodiment of thepresent invention, a mobile station is capable of communicating throughmore than one wireless network to the location server when in thecoverage area of these wireless networks. However, the trade-off betweencost and performance may dictate communication with the server using oneof the wireless networks, while using the others only for timingmeasurements (or other measurements, such as received signal levels) orfor aiding in measurement, such as obtaining time information fromwireless transmission from an access point for time stampingmeasurements (e.g., for resolving ambiguity), or locking to the accuratecarrier frequency of a wireless cellular base station for calibratingthe local oscillator of the mobile station.

In one embodiment of the present invention, the location of the mobilestation is determined at the location server using the informationcommunicated from the mobile station and then transmitted back to themobile station. Alternatively, the position calculation can be performedat the mobile station using assistance information from the locationserver (e.g., Doppler frequency shifts for in view satellites, positionsand coverage areas of access points, differential GPS data, altitudeaiding information).

FIG. 5 shows another example of a hybrid positioning system according toone embodiment of the present invention. An access point of one wirelessnetwork (e.g., cellular base station 503) is used for the communicationbetween mobile station 507 and location server 511. A method fordetermining the position of mobile station 507 may use SPS signals(e.g., from satellite 521), wireless signals from the access points(e.g. cellular phone base station 503) of the wireless network used fordata communication, as well as the wireless signals from access pointsof other wireless networks, such as those from access point B (505),which can be a base station of a different wireless cellular phonenetwork (e.g., operated by a different service provider, or using adifferent air interface), and from access point A (509), which can be awireless LAN access point (e.g., a bluetooth access point or a Wi-Fiwireless access point).

Typically, a wireless LAN access point (or other similar low powertransmitters) has a small coverage area. When available, the smallcoverage area of such an access point provides a very good estimate ofthe location of the mobile station. Further, wireless LAN access pointsare typically located near or inside buildings, where the availabilityof other types of signals (e.g., SPS signals or wireless telephonesignals) may be low. Thus, when such wireless transmissions are usedwith other types of signals, the performance of the positioning systemcan be greatly improved.

In one embodiment of the present invention, the wireless signals fromdifferent wireless networks are used for position determination. Forexample, the wireless signals from the different wireless networks canbe used to determine the identities of the corresponding access points,which are then used to determine the locations and coverage areas of thecorresponding access points. When precision range information (e.g.,round trip time or signal traveling time between an access point and themobile station) is available, the range information and the location ofthe access point can be used in obtaining a hybrid positioning solution.When approximate range information (e.g., received signal level, whichcan be approximately correlated with an estimated range) is available,the location of the access point can be used to estimate the position ofthe mobile station (or determine the estimated altitude of the mobilestation). Further, the mobile station can use precision carrierfrequency from one of the wireless networks (e.g., from access point 505or 509), which may not be the one used for the data communicationpurpose, to calibrate the local oscillator of the mobile station. Moredetails about locking to a precision carrier frequency of a wirelesssignal to provide a reference signal at an SPS receiver for signalacquisition can be found in U.S. Pat. No. 5,874,914. Further, the mobilestation can use the accurate time information in the wireless signalsfrom one of the wireless networks (e.g., from access point 505 or 509),which may not be the one used for the data communication purpose. Moredetails about using the accurate time information (e.g., timing markers,or system time) for time stamping can be found in U.S. Pat. No.5,945,944.

Since some of the access points of the different wireless networks donot have well-known almanac data (e.g., position of the wireless accesspoint, coverage area of the wireless access point), one embodiment ofthe present invention derives the almanac data from the informationcollected from mobile stations. FIG. 6 illustrates one method todetermine the position of a wireless access point according to oneembodiment of the present invention. In FIG. 6, a location server doesnot know the position of access point antenna 601. To calculate theposition of the access point, the location server correlates thepositions of one or more mobile stations and their corresponding rangesto the access point, which are obtained from the mobile stations whileperforming position determination for the mobile stations. For example,a mobile station at position L₁ (611) determines range R₁ (613) toaccess point antenna 601. The mobile station obtains measurements basedon SPS signals (e.g. measurements of SPS pseudoranges and extraction ofSPS ephemeris information from SPS signals) and wireless transmissions(e.g. range measurements). The mobile station may calculate its positionusing the measurements and transmit to the location server thecalculated position with: i) the range to the access point antenna; and,ii) the identity of the access point antenna. Alternatively, the mobilestation may transmit: i) the measurements; ii) the range to the accesspoint antenna; and, iii) the identity of the access point antenna to thelocation server, which calculates the position of the mobile stationusing the measurements and which stores the range measurements (e.g. R₁,R₂ and R₃ and the corresponding positions (e.g. L₁, L₂, and L₃). When anumber of data points are available, each of which data pointscorrelates the position of a mobile station and the range from themobile station to the access point antenna, the location serverdetermines the position of the access point antenna. It can be seen fromFIG. 6 that as few as three range measurements (R₁, R₂, and R₃) andtheir corresponding positions (L₁, L₂, and L₃) are sufficient to specifya particular location of the identified access point (which is shown atthe intersection of three circles specified by the three ranges).Various methods that have been used in the art for: calculating theposition of a mobile station based on range information can be used tocalculate the position of the access point. Note that the data pointsmay be from a single mobile station or from a number of mobile stations.

Further, the accumulated data points of the locations of mobile stationsshow the coverage area of the access point (e.g., in a scatter plot ofthe mobile locations). When the position of the access point is notknown, the collected data points can be used to estimate the positionand the coverage of the access point. When an initial estimation of theposition of the access point is available, the collected data points canbe used to improve the estimation. The collection and enhancementprocess can be a continuous process during the service of the locationserver. Note that the collection and enhancement operations can also beperformed on a different server other than the location server. Forexample, in one embodiment of the present invention, the collection andenhancement operations are performed in almanac server 513, whichcommunicates with location server 511 in performing hybrid positiondetermination for mobile stations.

However, precision information of range to some access points may not beavailable to mobile stations of a location server. FIG. 7 illustratesanother method to determine the position information of a wirelessaccess point according to one embodiment of the present invention. Alarger number of data points (e.g., 711, 713, 715, 721, 723, 725) of thelocations of mobile stations that can receive signals from the accesspoint (e.g., 703) define a coverage area (e.g., 705) of the access point(e.g., through a scatter plot of the locations, the smallest circleenclosing the data points). From the coverage area, the location servercan calculate an estimated position of the access point (e.g., thegeometric center of the coverage area). Further, range information(e.g., an indicator of the received signal level, a round trip time) maybe used to define a weight for determining the weighted average of thecoverage area (e.g., the closer to the access point, the larger theweight), from which the estimated position of the access point isdetermined. Further, in one embodiment, the location server determinesthe probability of a mobile station being at a particular location fromthe statistics of the mobile stations, given certain range informationis specified. Other information, such as the signal level of wirelesstransmission from other transmitters, can then be further used to narrowthe possible locations of the mobile station.

For example, a wireless LAN access point is located inside building 701.While SPS signals (e.g., signals from SPS satellites 741-745) andwireless cellular phone signals (e.g., signals from cellular basestation 751) may be weak inside building 701, the position of a mobilestation can be easily determined (e.g., without using the signals fromaccess point 703) at certain locations around the building (e.g.,locations 711-725, which may be just outside the building or at certainlocations inside the building, such as spots close to windows). In oneembodiment of the present invention, the identification of the accesspoint is determined and sent to the server with the location of themobile station (or information specifying the location of the mobile,such as pseudoranges to in view satellites) for the determination of thecoverage area (and/or the position) of the access point 703. Thelocation information of the access point (e.g., coverage area, position)can be maintained at the server (or a different server). When a mobilestation is inside a building (or at a position near the building), wherethe blockage of some of the SPS signals and cellular phone signalsoccurs, the location information about the access point can be used toaid in determining the position of the mobile station.

It is understood that some access points may be moved from one locationto another. In one embodiment of the present invention, the servertracks the collected position information about one or more mobilestations that receive the transmission from one access point in order todetermine if the access point is moved. For example, the server maycompare the old coverage area with the recent coverage area (e.g.,through comparing the center and the radius of the coverage area) todetermine if the access point is moved. Alternatively, the server mayperiodically discard old information in view of newly collectedinformation. Further, the server may weight the collected information sothat the freshly collected data carries more weight in determining thecoverage area and/or the location of the access point and the influencefrom the data collected previously may eventually diminish over time.Further, the server may determine if an access point moves frequently;and, if the access point moves frequently, the access point may bedisqualified as a reference point for the position determination.Further, in one embodiment, when an access point has not been observedfor a certain period of time, the access point is removed from thedatabase; similarly, when a new access point is observed, it is added tothe database. Thus, the server may update the information about theaccess point in an ongoing basis.

In at least one embodiment of the present invention, a mobile stationcan determine its position without a communication link. The mobilestation has memory for storing at least some of the information aboutthe locations of the mobile station and the corresponding receivedsignal levels or range measurements of a number of wireless accesspoints (e.g., for cellular phone access, or for wireless LAN access).The mobile station transmits the data to a server when a communicationlink (e.g., a wire connection through a communication port of the mobilestation or a wireless connection through a transceiver of the mobilestation) is available. Alternatively, the mobile station may directlyuse the stored information to derive the position information about theaccess point in determining its own position when needed.

FIG. 8 shows a general method of hybrid position determination using aplurality of wireless networks according to one embodiment of thepresent invention. In operation 801, a mobile station receives wirelesssignals transmitted from a plurality of wireless access points ofdifferent wireless networks (e.g., wireless networks of different airinterfaces, wireless networks of different service providers, wirelessnetworks operating at different frequencies, wireless networks usingdifferent communication protocols, etc.). In operation 803, the mobilestation utilizes the wireless signals from each of the access points ofthe different wireless networks in determining the position of themobile station (e.g., to determine the identity of the access point, tolock a local oscillator of the mobile station to a precision carrierfrequency of a wireless signal, to obtain a timing indicator from awireless signal, to determine signal transmission delay between themobile station and one of the access points, to communicate with aserver). In general, the mobile station may use the wireless signalsfrom access points of different wireless networks to perform differentoperations, although the mobile station may use the wireless signalsfrom access points of some different wireless networks to perform anumber of similar operations. In operation 805, the mobile stationcommunicates with a server to determine the position of the mobilestation using at least one of the different wireless networks.Typically, the mobile station communicates with the server using onlyone of the different wireless networks; however, the mobile station maycommunicate with the server using more than one wireless network (e.g.,to transmit the time of reception at an access point for a signaltransmitted from the mobile station, to transmit a round trip time, orto transmit other information to or from a location server).

FIG. 9 shows a method of hybrid position determination using twowireless networks for communication with a server according to oneembodiment of the present invention. Operation 821 receives, at a mobilestation, SPS signals transmitted from one or more SPS satellites andwireless signals transmitted from a plurality of wireless access pointsof more than one wireless network. The mobile station may use thereceived wireless signals from one or more wireless networks to aid inSPS signal acquisitions (e.g., to extract Doppler frequency shifts forin view satellites of the mobile station, to calibrate the localoscillator of the mobile station, to obtain a timing indicator to timestamp a measurement). The mobile station uses the SPS signals todetermine pseudoranges to in view satellites, and the mobile stationuses wireless signals from the wireless access points to identify theaccess points and to perform range measurements to the wireless accesspoints for position determination. These received signals are typicallybroadcast from the transmitters of the satellites and wireless accesspoints and available to any mobile station that chooses to use them.Operation 823 communicates first information (e.g., a record of an SPSmessage) between the mobile station and a server using an access pointof a first wireless network (e.g., a wireless local area network).Operation 825 communicates second information (e.g., Doppler frequencyshifts, ephemeris data for in view SPS satellites) between the mobilestation and a server using an access point of a second wireless network(e.g., a wireless cellular phone network). Operation 827 determines theposition of the mobile station from the communication of the firstinformation and the second information. Typically, the availability,coverage, expense, data speed, and ease of use are considered whenchoosing which communications path to use. Further, the mobile stationmay use different communication paths at different locations. Forexample, when the mobile station is within the coverage area of awireless LAN (e.g., a home network), the mobile station may use thewireless LAN (e.g., through internet) to communicate with the server forinformation that does not need to pass through the base station of awireless cellular phone system (e.g., Doppler frequency shifts); and,use the base station of the wireless cellular phone system to transmitthe information that is related to the base station (e.g., round triptime measurement to the base stations of the wireless cellular phonesystem). In a further example, the mobile station may choose to useeither the wireless cellular phone system or the wireless LAN forcommunication according to the communication cost and availability. Inone embodiment of the present invention, the mobile stationautomatically determines the communication path according to a set ofrules (e.g., availability, cost, priority, and others) which may bespecified by a user of the mobile station or may be set as a defaultsetting by one of the wireless networks.

FIG. 10 shows a method to generate location information about a wirelessaccess point according to one embodiment of the present invention.Operation 841 detects, at a mobile station, wireless signals transmittedfrom a wireless access point (e.g., a wireless access point that is incompliance with the IEEE 802.11 standard for wireless local areanetwork, or other types of ground-based wireless transmitters thattransmit signals with their identification information). Note that, inthe present application, wireless access points do not includesatellite-based transmitters. Operation 843 determines identificationinformation, which may be a unique identifier, of the wireless accesspoint (e.g., the MAC address of the wireless access point or anidentifier of a cellular base station) from the wireless signals.Operation 845 determines the position of the mobile station (e.g., atthe mobile station or at a location server). For example, the mobilestation may calculate the position based on the pseudorange measurementsand other range information; or, the mobile station may transmit thepseudorange measurements and the range information to a location server,which calculates the position of the mobile station (and, the locationserver may send back the calculated position to the mobile station).Operation 847 correlates the position of the mobile station with theidentification information of the wireless access point. Thiscorrelation may be transmitted to a location server so that futurepositioning operations of mobile stations may use the position andidentification information to determine a position of the identifiedwireless access point. Operation 849 generates location informationabout the wireless access point (e.g., access point almanac, statisticsof coverage area of the wireless access point). Typically, thecorrelation data is sent to a server (e.g., a location server, or anaccess point almanac server) which generates location information aboutthe access point based on a number of positions of one or more mobilestations that report the reception of signals transmitted from theaccess point. The location information about the wireless access pointcan be derived from a weighted average method as described above (orother methods, such as, using the range information as shown in FIG. 6).However, a mobile station may also track the correlation and derive thelocation information about the wireless access point (e.g., from datapoints collected at different time instances). The location informationabout the wireless access point can then be used for positiondetermination.

FIG. 11 shows a hybrid position determination method using one wirelessnetwork for communication and another wireless network for themeasurement of positioning parameters according to one embodiment of thepresent invention. Operation 861 detects, at a mobile station, wirelesssignals transmitted from a wireless access point (e.g., a wirelessaccess point that is in compliance with the IEEE 802.11 standard forwireless local area network, or a cellular communication base station)of a first wireless network (e.g., a wireless local area network, or acellular phone communication system). Operation 863 determines theidentification information of the wireless access point (e.g., the MACaddress, or the base station ID) from the wireless signals. Operation865 retrieves location information about the wireless access point(e.g., access point almanac) using the identification information. Forexample, the mobile station may transmit identification information ofthe wireless access point to location server, which retrieves thelocation information about the wireless access point using theidentification information (e.g., from a database, or from anotherserver, such as an access point almanac server). In another example, themobile station maintains the location information about the wirelessaccess point in memory; thus, the location information is simplyretrieved from the memory of the mobile station. Operation 867determines the position of the mobile station using the locationinformation and using a communication link between the mobile stationand a wireless access point of a second wireless network (e.g., acellular phone network). For example, satellite assistance data (e.g.,Doppler frequency shifts) for the acquisition of SPS signals or timingmeasurements (e.g., pseudoranges or time of arrivals of SPS signals) arecommunicated through the second wireless network for the determinationof the position of the mobile station.

FIG. 12 shows another exemplary method of the inventions. In thismethod, a mobile station receives, in operation 901, first signalstransmitted from a first wireless access point of a first wirelessnetwork. The first wireless network may support two-way communicationbetween the various nodes within the first wireless network as well asnodes outside of this network. In operation 903, at least one rangemeasurement is determined using the first signals. If additional signalsfrom other wireless access points of the first wireless network are alsoavailable, then additional range measurements to these other wirelessaccess points (and their identification information) are obtained. In analternative implementation of operation 903, another measurement (e.g. asignal strength measurement of the first signals) may be taken by themobile station without attempting to make a range measurement using thefirst signals. In one exemplary implementation, a time of travel of thefirst signals from the first wireless access point to the mobile stationis measured and an identification of this first wireless access point isreceived from the first wireless access point. In operation 905, secondsignals are communicated between the mobile station and a secondwireless access point of a second wireless network, which is differentthan the first wireless network. The mobile station may, in thisoperation, receive the second signals (which may include SPS assistancedata, etc.) from the second wireless access point. In operation 907, themobile station and the server communicate to determine the position ofthe mobile station, and this communication may be through the secondwireless access point. For example, the mobile station may, in operation907, transmit the range measurements and identification information,performed in operation 903, and SPS pseudoranges, obtained by the mobilestation, to the server through the second wireless access point. Theidentification information is used to obtain the location of thewireless access points to which range measurements (or othermeasurements) were obtained, and the server may then determine theposition of the mobile station using at least some of the availablemeasurements (e.g. the SPS pseudoranges to SPS satellites and the rangemeasurements, or other measurements, to various terrestrial wirelessaccess points). Alternatively, the mobile station may determine itsposition (rather than the server doing so) using the range measurementsand SPS pseudo ranges and using information provided by the server (suchas the location of the identified wireless access points in one or bothof the wireless networks).

The first wireless network in FIG. 12 may be a wireless local areanetwork and, in this case, the first wireless access point may be awireless router operating according to a Wi-Fi standard. Alternatively,the first wireless network may be a wireless cellular telephone networkoperated by a first service provider, and the second wireless networkmay be another (different) wireless cellular telephone network operatedby a second service provider, and the mobile station, which may be acellular telephone with an integrated GPS receiver, is authorized tooperate with only the second wireless network and not the first wirelessnetwork. Various other alternatives, discussed herein, may also apply tothis example of FIG. 12.

FIG. 13 is another example of a method of the inventions. In thisexample, the mobile station, in operation 931, obtains an identificationinformation of a first wireless access point of a first wireless networkthat is accessible (e.g. within radio communication) to the mobilestation. This identification may be a MAC address (e.g. for an Ethernetlocal area network) or a cellular telephone base station (e.g. “celltower”) identifier. In operation 933, the mobile station transmits,through a second wireless access point of a second wireless network, theidentification information to a server (e.g. a location server) during aposition determination operation. In this example, the second wirelessnetwork is different than the first wireless network (e.g. different airinterfaces, different service providers, etc.). Then, in operation 935,the server uses the identification information of the first wirelessaccess point to determine the location of the first wireless accesspoint (which may have been harvested/collected through methods describedherein, such as in FIG. 14). The server may also, in operation 935, useother data (e.g. SPS pseudoranges determined at a GPS receiver which isintegrated into the mobile station and then transmitted to the server)to determine the position of the mobile station. The server may, forexample, combine the SPS pseudoranges with the measurements on signalsfrom the wireless access points to determine the position of the mobilestation. Alternatively, the SPS pseudoranges may be combined with theknown locations of the wireless access points (particularly in the caseof wireless LANs which have shorter signal ranges). In anotheralternative to operation 935, the server may provide assistance data(e.g. the location of the first wireless access point and possibly otherdata such as Doppler data for SPS satellites in view of the mobilestation, etc.) to the mobile station but the server does not compute theposition of the mobile station; rather, the mobile station performs theposition solution using at least some of the available measurements(e.g. SPS pseudoranges, range measurements or other measurementsrelative to the wireless access points of one or all available wirelessnetworks) and the available assistance data from the server.

FIG. 14 shows another exemplary method of the inventions. This methodultimately determines positions of wireless access points so that futureposition determination operations for mobile stations can be performedusing multiple wireless networks as described herein. In operation 971,data is collected. This data specifies a plurality of locations ofmobile stations at which wireless signals, transmitted from at least afirst wireless access point of a first wireless network, are receivedduring determinations of the plurality of locations. The mobile stationsmay, in operation 973, receive signals from the first wireless accesspoints and also communicate signals between the mobile stations and atleast one second wireless access point of a second wireless network(which is different than the first wireless network). This communicationwith the second wireless network may be for the purpose of providinginformation used in collecting the data which is used to determine thelocations of wireless access points of the first wireless network. Inoperation 975, the location of at least the first wireless access pointis determined (e.g. in the manner shown in FIG. 6) from the coveragearea defined by the plurality of locations.

FIG. 2 shows an example of a data processing system which may be used asa server in various embodiments of the present invention. For example,as described in U.S. Pat. No. 5,841,396, the server (201) may provideassistance data such as Doppler or other satellite assistance data tothe GPS receiver in a mobile station. In addition, or alternatively, thesame server or a different server may perform the final positioncalculation rather than the mobile station (after receiving pseudorangesor other data from which pseudoranges can be determined from the mobilestation) and then may forward this position determination result to thebase station or to some other system. The data processing system as aserver (e.g., a location server, an almanac server) typically includescommunication devices 212, such as moderns or network interface. Thelocation server may be coupled to a number of different networks throughcommunication devices 212 (e.g., modems or other network interfaces).Such networks include one or more intranets, the network, the cellularswitching center or multiple cellular switching centers 225, the landbased phone system switches 223, cellular base stations (not shown inFIG. 2), GPS receivers 227, or other processors or location servers 221.

Multiple cellular base stations are typically arranged to cover ageographical area with radio coverage, and these different base stationsare coupled to at least one mobile switching center, as is well known inthe prior art (e.g., see FIG. 1). Thus, multiple base stations would begeographically distributed but coupled together by a mobile switchingcenter. The network 220 may be connected to a network of reference GPSreceivers which provide differential GPS information and may alsoprovide GPS ephemeris data for use in calculating the position of mobilesystems. The network is coupled through the modem or other communicationinterface to the processor 203. The network 220 may be connected toother computers or network components. Also network 220 may be connectedto computer systems operated by emergency operators, such as the PublicSafety Answering Points which respond to 911 telephone calls. Variousexamples of methods for using a location server have been described innumerous U.S. patents, including: U.S. Pat. Nos. 5,841,396, 5,874,914,5,812,087 and 6,215,442.

The server 201, which is a form of a data processing system, includes abus 202 which is coupled to a microprocessor 203 and a ROM 207 andvolatile RAM 205 and a non-volatile memory 206. The processor 203 iscoupled to cache memory 204 as shown in the example of FIG. 2. The bus202 interconnects these various components together. While FIG. 2 showsthat the non-volatile memory is a local device coupled directly to therest of the components in the data processing system, it will beappreciated that the present invention may utilize a non-volatile memorywhich is remote from the system, such as a network storage device whichis coupled to the data processing system through a network interfacesuch as a modem or Ethernet interface. The bus 202 may include one ormore buses connected to each other through various bridges, controllersand/or adapters as is well known in the art. In many situations thelocation server may perform its operations automatically without humanassistance. In some designs where human interaction is required, the I/Ocontroller 209 may communicate with displays, keyboards, and other I/Odevices.

Note that while FIG. 2 illustrates various components of a dataprocessing system, it is not intended to represent any particulararchitecture or manner of interconnecting the components as such detailsare not germane to the present invention. It will also be appreciatedthat network computers and other data processing systems which havefewer components or perhaps more components may also be used with thepresent invention and may act as a location server or a PDE (positiondetermination entity).

In some embodiments, the methods of the present invention may beperformed on computer systems which are simultaneously used for otherfunctions, such as cellular switching, messaging services, etc. In thesecases, some or all of the hardware of FIG. 2 would be shared for severalfunctions.

It will be apparent from this description that aspects of the presentinvention may be embodied, at least in part, in software. That is, thetechniques may be carried out in a computer system or other dataprocessing system in response to its processor executing sequences ofinstructions contained in memory, such as ROM 207, volatile RAM 205,non-volatile memory 206, cache 204 or a remote storage device. Invarious embodiments, hardwired circuitry may be used in combination withsoftware instructions to implement the present invention. Thus, thetechniques are not limited to any specific combination of hardwarecircuitry and software nor to any particular source for the instructionsexecuted by the data processing system. In addition, throughout thisdescription, various functions and operations are described as beingperformed by or caused by software code to simplify description.However, those skilled in the art will recognize what is meant by suchexpressions is that the functions result from execution of the code by aprocessor, such as the processor 203.

A machine readable medium can be used to store software and data whichwhen executed by a data processing system causes the system to performvarious methods of the present invention. This executable software anddata may be stored in various places including for example ROM 207,volatile RAM 205, non-volatile memory 206 and/or cache 204 as shown inFIG. 2. Portions of this software and/or data may be stored in any oneof these storage devices.

Thus, a machine readable medium includes any mechanism that provides(i.e., stores and/or transmits) information in a form accessible by amachine (e.g., a computer, network device, personal digital assistant,manufacturing tool, any device with a set of one or more processors,etc.). For example, a machine readable medium includesrecordable/non-recordable media (e.g., read only memory (ROM); randomaccess memory (RAM); magnetic disk storage media; optical storage media;flash memory devices; etc.), as well as electrical, optical, acousticalor other forms of propagated signals (e.g., carrier waves, infraredsignals, digital signals, etc.); etc.

FIG. 3 shows a block diagram representation of a mobile stationaccording to one embodiment of the present invention. The mobile stationincludes a portable receiver, which combines a communication transceiverwith GPS receiver for use in one embodiment of the present invention.The combined mobile unit 310 includes circuitry for performing thefunctions required for processing GPS signals as well as the functionsrequired for processing communication signals received through acommunication link. The communication link, such as communication link350 or 360, is typically a radio frequency communication link to anothercomponent, such as base station 352 having communication antenna 351 orwireless LAN access point 362 with antenna 361. Although FIG. 3illustrates an embodiment that communication antenna 311 is used forreceiving signals from different types of wireless access points (e.g.,from access point 362 for wireless LAN and from based station 352 forcellular phone service), the combined receiver may use separate anddistinct antennas for receiving signals of different air interfaces.Further, the combined receiver may use separate and distinct componentsfor at least a partial processing of the received wireless signals andmay or may not share some components in the processing of the wirelesssignals of different air interfaces. For example, the combined receivermay have separate circuits for the RF signal processing and share samedata processor resources. From this description, various combinationsand variations of the combined receiver will be apparent to one skilledin the art.

Portable receiver 310 is an example of a combined GPS receiver and acommunication receiver and transmitter. The communication receiver andtransmitter may be implemented as multiple receivers and transmittersfor the different wireless networks. For example, the communicationtransceiver 305 may include a transceiver portion for receiving and/ortransmitting cellular telephone signals and another transceiver portionfor receiving and/or transmitting Wi-Fi signals. Receiver 310 contains aGPS receiver stage including acquisition and tracking circuit 321 andcommunication transceiver section 305. Acquisition and tracking circuit321 is coupled to GPS antenna 301, and communication transceiver 305 iscoupled to communication antenna 311. GPS signals (e.g., signal 370transmitted from satellite 303) are received through GPS antenna 301 andinput to acquisition and tracking circuit 321 which acquires the PN(Pseudorandom Noise) codes for the various received satellites. The dataproduced by circuit 321 (e.g., correlation indicators) are processed byprocessor 333 for transmittal {e.g. of SPS pseudoranges) by transceiver305. Communication transceiver 305 contains a transmit/receive switch331 which routes communication signals (typically RF) to and fromcommunication antenna 311 and transceiver 305. In some systems, a bandsplitting filter, or “duplexer,” is used instead of the T/R switch.Received communication signals are input to communication receiver 332and passed to processor 333 for processing. Communication signals to betransmitted from processor 333 are propagated to modulator 334 andfrequency converter 335. Power amplifier 336 increases the gain of thesignal to an appropriate level for transmission to base station 352 (orto wireless LAN access point 362).

In one embodiment of the present invention, communication transceiversection 305 is capable of being used with a number of different airinterfaces (e.g., IEEE 802.11, bluetooth, UWB, TD-SCDMA, IDEN, HDR,TDMA, GSM, CDMA, W-CDMA, UMTS, or other similar networks) forcommunication (e.g., through communication links 350 and 360). In oneembodiment of the present invention, communication transceiver section305 is capable of being used with one air interface for communicationand capable of being used to receive signals with other air interfaces.In one embodiment of the present invention, communication transceiversection 305 is capable of being used with one air interface forcommunication while also being capable of being used with signals inanother air interface to extract timing indicators (e.g., timing framesor system time) or to calibrate the local oscillator (not shown in FIG.3) of the mobile station. More details about the mobile station forextracting timing indicators or calibrating the local oscillator can befound in U.S. Pat. Nos. 5,874,914 and 5,945,944.

In one embodiment of the combined GPS/communication system of receiver310, data generated by acquisition and tracking circuit 321 istransmitted to a server over communication link 350 to base station 352or over communication link 360 to wireless LAN access point 362. Theserver then determines the location of receiver 310 based on the datafrom the remote receiver, the time at which the data were measured, andephemeris data received from its own GPS receiver or other sources ofsuch data. The location data can then be transmitted back to receiver310 or to other remote locations. More details about portable receiversutilizing a communication link can be found in U.S. Pat. No. 5,874,914.

In one embodiment of the present invention, the combined GPS receiverincludes (or is coupled to) a data processing system (e.g., a personaldata assistant, or a portable computer). The data processing systemincludes a bus which is coupled to a microprocessor and a memory (e.g.,ROM, volatile RAM, non-volatile memory). The bus interconnects variouscomponents together and also interconnects these components to a displaycontroller and display device and to peripheral devices such asinput/output (I/O) devices, which are well known in the art. The bus mayinclude one or more buses connected to each other through variousbridges, controllers and/or adapters as are well known in the art. Inone embodiment, the data processing system includes communication ports(e.g., a USB (Universal Serial Bus) port, a port for IEEE-1394 busconnection). In one embodiment of the present invention, the mobilestation stores the locations and identifications (e.g., MAC address) ofwireless access points (e.g., according to the types of the wirelessaccess points) for extracting and enhancing the location informationabout the wireless access points using the memory and software programinstructions stored in the memory. In one embodiment, the mobile stationonly stores the locations of the mobile station and identifications ofthe wireless access points for transmission to a server (e.g., through acommunication port, or a wireless communication link) when acommunication connection is established.

Although the methods and apparatus of the present invention have beendescribed with reference to GPS satellites, it will be appreciated thatthe descriptions are equally applicable to positioning systems whichutilize pseudolites or a combination of satellites and pseudolites.Pseudolites are ground-based transmitters which broadcast a PN code(similar to a GPS signal), typically modulated on an L-band carriersignal, generally synchronized with GPS time. Each transmitter may beassigned a unique PN code so as to permit identification by a remotereceiver. Pseudolites are useful in situations where GPS signals from anorbiting satellite might be unavailable, such as tunnels, mines,buildings or other enclosed areas. The term “satellite”, as used herein,is intended to include pseudolites or equivalents of pseudolites, andthe term GPS signals, as used herein, is intended to include GPS-likesignals from pseudolites or equivalents of pseudolites.

In the preceding discussion the invention has been described withreference to application upon the United States Global PositioningSatellite (GPS) system. It should be evident, however, that thesemethods are equally applicable to similar satellite positioning systems,and in particular, the Russian GLONASS system and the proposed EuropeanGalileo System. The GLONASS system primarily differs from GPS system inthat the emissions from different satellites are differentiated from oneanother by utilizing slightly different carrier frequencies, rather thanutilizing different pseudorandom codes. In this situation substantiallyall the circuitry and algorithms described previously are applicable.The term “GPS” used herein includes such alternative satellitepositioning systems, including the Russian GLONASS system, and theEuropean Galileo System.

Although the operations in the above examples are illustrated inspecific sequences, from this description, it will be appreciated thatvarious different operation sequences and variations can be used withouthaving to be limited to the above illustrated examples.

The above examples are illustrated without presenting some of thedetails known in the art; as pointed out in the above discussion, thesedetails can be found in publications, such as U.S. Pat. Nos. 5,812,087,5,841,396, 5,874,914, 5,945,944, 5,999,124, 6,061,018, 6,208,290, and6,215,442, all of which are hereby incorporated here by reference.

In the foregoing specification, the invention has been described withreference to specific exemplary embodiments thereof. It will be evidentthat various modifications may be made thereto without departing fromthe broader spirit and scope of the invention as set forth in thefollowing claims. The specification and drawings are, accordingly, to beregarded in an illustrative sense rather than a restrictive sense.

What is claimed is:
 1. A method for location determination, the methodcomprising: receiving, by a first mobile station, during a first timeperiod, satellite positioning system (SPS) signals from SPS satellites;determining, by the first mobile station during the first time period,one or more positions of the first mobile station based on the receivedSPS signals; receiving, by the first mobile station, at the one or morepositions of the first mobile station during the first time period,first wireless signals from a first access point of a first wirelessnetwork, wherein the first wireless signals received from the firstwireless access point comprise identification information of the firstwireless access point, wherein the first wireless network is a wirelesslocal area network (WLAN), and wherein the first mobile station is notauthorized to have access to the first wireless network; transmitting,from the first mobile station to a location server, informationcomprising the one or more positions of the first mobile station and theidentification information of the first wireless access point;receiving, by a second mobile station, during a second time period afterthe first time period, second wireless signals from the first accesspoint, wherein the second wireless signals comprise the identificationinformation of the first wireless access point; determining, by thesecond mobile station, positioning information with respect to the firstwireless access point using the second wireless signals received fromthe first wireless access point, the positioning information comprisingsignal strength measurements, timing measurements, or both;transmitting, from the second mobile station to the location server,information comprising the identification information of the firstwireless access point; receiving, at the second mobile station, from thelocation server, location information of the first wireless accesspoint; and determining, by the second mobile station, a position of thesecond mobile station using the location information received from thelocation server and the positioning information.
 2. The method of claim1, wherein the first mobile station is the same as the second mobilestation.
 3. The method of claim 1, wherein the first mobile station isdifferent than the second mobile station.
 4. The method of claim 1,wherein the second mobile station is not authorized to have access tothe first wireless network.
 5. The method of claim 1, wherein theinformation comprising the one or more positions of the first mobilestation and the identification information of the first wireless accesspoint are transmitted from the first mobile station to the locationserver via a cellular base station of a cellular network.
 6. The methodof claim 1, wherein the information comprising the identification of thefirst wireless access point is transmitted from the second mobilestation to the location server via a cellular base station of a cellularnetwork.
 7. The method of claim 1, further comprising storing, at thefirst mobile station, the one or more positions of the first mobilestation and the identification information of the first wireless accesspoint, and transmitting, from the first mobile station, the informationcomprising the one or more positions of the first mobile station and theidentification information of the first wireless access point after acommunication connection between the first mobile station and locationserver has been established.
 8. The method of claim 7, furthercomprising transmitting, from the first mobile station, informationcomprising one or more additional positions of the first mobile stationand identification information of one or more additional wireless accesspoints after the communication connection has been established.
 9. Themethod of claim 1, wherein determining the position of the second mobilestation is additionally based on signals from a second wireless accesspoint of a second wireless network.
 10. The method of claim 9, whereinthe second wireless access point comprises a cellular base station andthe second wireless network comprises a cellular network.
 11. The methodof claim 1, wherein the identification information of the first wirelessaccess point comprises a Media Access Control (MAC) address or anInternet Protocol (IP) address.
 12. A system for location determination,the system comprising: a first mobile station comprising: a firsttransceiver; a first memory; and a first processor, wherein the firstprocessor is communicatively coupled with the first transceiver and thefirst memory and configured to: receive, via the first transceiver,during a first time period, satellite positioning system (SPS) signalsfrom SPS satellites; determine, during the first time period, one ormore positions of the first mobile station based on the received SPSsignals; receive, via the first transceiver, at the one or morepositions of the first mobile station during the first time period,first wireless signals from a first access point of a first wirelessnetwork, wherein the first wireless signals received from the firstwireless access point comprise identification information of the firstwireless access point, wherein the first wireless network is a wirelesslocal area network (WLAN), and wherein the first mobile station is notauthorized to have access to the first wireless network; and transmit,via the first transceiver to a location server, information comprisingthe one or more positions of the first mobile station and theidentification information of the first wireless access point; and asecond mobile station comprising: a second transceiver; a second memory;and a second processor, wherein the second processor is communicativelycoupled with the second transceiver and the second memory and configuredto: receive, via the second transceiver, during a second time periodafter the first time period, second wireless signals from the firstaccess point, wherein the second wireless signals comprise theidentification information of the first wireless access point; determinepositioning information with respect to the first wireless access pointusing the second wireless signals received from the first wirelessaccess point, the positioning information comprising signal strengthmeasurements, timing measurements, or both; transmit, via the secondtransceiver, to the location server, information comprising theidentification information of the first wireless access point; receive,via the second transceiver, from the location server, locationinformation of the first wireless access point; and determine a positionof the second mobile station using the location information receivedfrom the location server and the positioning information.
 13. The systemof claim 12, wherein the second mobile station is not authorized to haveaccess to the first wireless network.
 14. The system of claim 12,wherein the first processor is further configured to transmit, via thefirst transceiver, the information comprising the one or more positionsof the first mobile station and the identification information of thefirst wireless access point to the location server via a cellular basestation of a cellular network.
 15. The system of claim 12, wherein thesecond processor is further configured to transmit, via the secondtransceiver, the information comprising the identification of the firstwireless access point to the location server via a cellular base stationof a cellular network.
 16. The system of claim 12, wherein the firstprocessor is configured to store, in the first memory, the one or morepositions of the first mobile station and the identification informationof the first wireless access point, and wherein the first processor isfurther configured to transmit, via the first transceiver, theinformation comprising the one or more positions of the first mobilestation and the identification information of the first wireless accesspoint after a communication connection between the first mobile stationand location server has been established.
 17. The system of claim 16,wherein the first processor is configured to transmit, via the firsttransceiver, information comprising one or more additional positions ofthe first mobile station and identification information of one or moreadditional wireless access point after the communication connection hasbeen established.
 18. The system of claim 12, wherein the secondprocessor is configured to determine the position of the second mobilestation additionally based on signals from a second wireless accesspoint of a second wireless network.
 19. The system of claim 18, whereinthe second wireless access point comprises a cellular base station andthe second wireless network comprises a cellular network.
 20. The systemof claim 12, wherein the identification information of the firstwireless access point comprises a Media Access Control (MAC) address oran Internet Protocol (IP) address.
 21. A system of locationdetermination, the system comprising: means for receiving, by a firstmobile station, during a first time period, satellite positioning system(SPS) signals from SPS satellites; means for determining, by the firstmobile station during the first time period, one or more positions ofthe first mobile station based on the received SPS signals; means forreceiving, by the first mobile station, at the one or more positions ofthe first mobile station during the first time period, first wirelesssignals from a first access point of a first wireless network, whereinthe first wireless signals received from the first wireless access pointcomprise identification information of the first wireless access point,wherein the first wireless network is a wireless local area network(WLAN), and wherein the first mobile station is not authorized to haveaccess to the first wireless network; means for transmitting, from thefirst mobile station to a location server, information comprising theone or more positions of the first mobile station and the identificationinformation of the first wireless access point; means for receiving, bya second mobile station, during a second time period after the firsttime period, second wireless signals from the first access point,wherein the second wireless signals comprise the identificationinformation of the first wireless access point; means for determining,by the second mobile station, positioning information with respect tothe first wireless access point using the second wireless signalsreceived from the first wireless access point, the positioninginformation comprising signal strength measurements, timingmeasurements, or both; means for transmitting, from the second mobilestation to the location server, information comprising theidentification information of the first wireless access point; means forreceiving, at the second mobile station, from the location server,location information of the first wireless access point; and means fordetermining, by the second mobile station, a position of the secondmobile station using the location information received from the locationserver and the positioning information.
 22. The system of claim 21,wherein the first mobile station is the same as the second mobilestation.
 23. The system of claim 21, wherein the second mobile stationis not authorized to have access to the first wireless network.
 24. Thesystem of claim 21, further comprising means for storing, at the firstmobile station, the one or more positions of the first mobile stationand the identification information of the first wireless access point,wherein the means for transmitting the information comprising the one ormore positions of the first mobile station and the identificationinformation of the first wireless access point are configured totransmit the information comprising the one or more positions of thefirst mobile station and the identification information of the firstwireless access point after a communication connection between the firstmobile station and location server has been established.
 25. The systemof claim 24, further comprising means for transmitting, from the firstmobile station, information comprising one or more additional positionsof the first mobile station and identification information of one ormore additional wireless access points after the communicationconnection has been established.
 26. The system of claim 21, furthercomprising means for determining the position of the second mobilestation additionally based on signals from a second wireless accesspoint of a second wireless network.
 27. The system of claim 26, whereinthe second wireless access point comprises a cellular base station andthe second wireless network comprises a cellular network.
 28. The systemof claim 21, wherein the identification information of the firstwireless access point comprises a Media Access Control (MAC) address oran Internet Protocol (IP) address.
 29. A non-transitorycomputer-readable medium storing instructions for locationdetermination, the instructions comprising code for: receiving, by afirst mobile station, during a first time period, satellite positioningsystem (SPS) signals from SPS satellites; determining, by the firstmobile station during the first time period, one or more positions ofthe first mobile station based on the received SPS signals; receiving,by the first mobile station, at the one or more positions of the firstmobile station during the first time period, first wireless signals froma first access point of a first wireless network, wherein the firstwireless signals received from the first wireless access point compriseidentification information of the first wireless access point, whereinthe first wireless network is a wireless local area network (WLAN), andwherein the first mobile station is not authorized to have access to thefirst wireless network; transmitting, from the first mobile station to alocation server, information comprising the one or more positions of thefirst mobile station and the identification information of the firstwireless access point; receiving, by a second mobile station, during asecond time period after the first time period, second wireless signalsfrom the first access point, wherein the second wireless signalscomprise the identification information of the first wireless accesspoint; determining, by the second mobile station, positioninginformation with respect to the first wireless access point using thesecond wireless signals received from the first wireless access point,the positioning information comprising signal strength measurements,timing measurements, or both; transmitting, from the second mobilestation to the location server, information comprising theidentification information of the first wireless access point;receiving, at the second mobile station, from the location server,location information of the first wireless access point; anddetermining, by the second mobile station, a position of the secondmobile station using the location information received from the locationserver and the positioning information.
 30. The non-transitorycomputer-readable medium of claim 29, wherein the first mobile stationis the same as the second mobile station.